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Math Help - I'm a dunce

  1. #1
    Newbie
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    Nov 2008
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    I'm a dunce

    This question is giving me a headache, and it's for homework. I usually can do these kinds of questions, but I feel really unmotivated right now.. Someone can help me solve it so I can see again..

    Find the equations of the focal chord that cuts the curve x^2=8y at (-4, 2)
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  2. #2
    Super Member

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    Lexington, MA (USA)
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    Hello, Cataclysm!

    If you made a sketch, the answer is obvious . . .


    Find the equation of the focal chord that cuts the curve x^2\:=\:8y at (-4, 2)
    From the equation, x^2 \:=\:8y, we know all this:
    . . The parabola opens upward.
    . . Its vertex is at the origin.
    . . The focus is at (0, 2).

    Code:
                    |
         *          |           *
                    |
          *        F|(0,2)     *
     (-4,2)*- - - - o - - - -*
             *      |      *
                *   |   *
        ------------*------------
                    |

    The focal chord that contains (-4, 2) is the horizonal line: .  y \:=\:2

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  3. #3
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    Joined
    Nov 2008
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    Yeah, that's what I thought it was, but I just couldn't explain myself properly. Thanks very much!
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